Which of the following statements about transportation costs are correct? Check all that apply. Over the past 50 years, transportation costs of U.S. imports have fallen to less than half of what they used to be, relative to the value of imports. _ International transportation costs are declining everywhere in the world. Transportation costs have recently become a larger expense for the global economy than was previously observed. _ Transportation costs are determined by the distance between two points, weight, size, value, and the volume of trade. _ Falling transportation costs reduce the volume of international trade by eliminating the basis for the growth of trade